The tola system
The tola was standardized in British India as 180 grains, which is 11.6638 grams. It is divided into 12 masha, and each masha into 8 ratti, so 1 tola = 96 ratti. Gold is still often discussed in tola, especially for older family jewellery, even though shops now weigh and price gold in grams.
Two different ratti: goldsmith and gemstone
The goldsmith (sunari) ratti is 1/96 tola, about 0.1215 grams. Gemstone sellers and astrologers usually use the pakki ratti, which is 1.5 goldsmith ratti, about 0.182 grams or 0.91 carat. That is why '1 ratti in carat' has two answers: about 0.61 carat for the goldsmith ratti and about 0.91 carat for the gemstone ratti. Always ask which ratti a seller means.
Seer, maund and quintal
In the standard British India system 1 seer = 80 tola = 0.933 kg, 1 maund = 40 seer = 37.32 kg, and 1 chhatak = 1/16 seer = 58.3 g. In everyday trade the maund is often rounded to 40 kg. The quintal, used for grain and crop prices, is exactly 100 kg — so 10 quintal make 1 metric tonne.
Worked examples
A 2-tola gold chain weighs 2 × 11.6638 = 23.33 grams. A 5-ratti gemstone (pakki ratti) is about 4.56 carats. A 2-maund bag of grain is about 74.6 kg in the standard maund, or 80 kg if your market uses the rounded 40 kg maund.